Growing cellular networks with millions of subscribers simultaneously hold a huge number of communication sessions which are often transmitted via mixed communication networks comprising both the cellular networks and various non-cellular networks.
IP (Internet Protocol) networks and Ethernet networks are digital communication networks that suit for the above purpose; they utilize digital packets of variable lengths capable of encapsulating data (such as contents of a communication session) for further transmission thereof in the network. The amount of real data (say, of the voice data) may form a tiny portion of a packet used for transporting the data. The packet can be IP in various modifications thereof, OSI, Ethernet, etc., but the problem remains the same.
In light of the above, the problem of compressing the lengthy packets becomes very actual to allow transmission of desired volumes of data, say originating from cellular networks, via non-cellular communications networks (for example, wireline, radio or any other non-cellular networks).
U.S. patent application 2004/0034708 describes a technology for fast Internet protocol headers compression initialization and also refers to a number of known methods of IP header compression (HC); the whole patent description is incorporated hereby by reference. A general approach to the IP packets compression by peeling and further restoring their headers is described in the detailed description with reference to FIG. 1. It should be noted that the mentioned compression/decompression of digital packets is specifically developed for a 3rd layer protocol according to the Open System Interconnection (OSI) model for communication networks.
A standardized technique of IP headers compression (HC) is described in 2507 [RFC] and referred to in the US 2004/0034708.
For Ethernet networks utilizing lower layer communications protocols (1st layer and 2nd layer) than the IP networks, no intrinsic compression/decompression technologies are presently known which would enable compression of Ethernet packets over an Ethernet link.
An Ethernet link is to be understood as a communication link between an Ethernet source node and an Ethernet destination node. It can be either a pure Ethernet link, or a combined communication link emulating the pure Ethernet link. One example of such an emulating link is a so-called Ethernet Private Line (EPL) according to (ITU G.8011, ITU G.8012) where the Ethernet source node and the Ethernet destination node are connected to one another via an intermediate non-Ethernet network portion of the OSI layer 1 or 2 by means of two Ethernet interfaces at the respective ends. The intermediate network portion may be, for example, a portion of the SONET/SDH network, a portion of a PDH network, an optical network, the media of the link may be a wire, an optical fiber (so-called dark fiber), radio or microwave. In the EPL, the Ethernet packets obtained from the source node are wholly mapped onto carrying blocks of the intermediate network, and then de-mapped from the carrying blocks to finally feed these Ethernet packets to the Ethernet destination node.
An Ethernet packet, in addition to its typical fields such as the payload and a number of Ethernet headers, comprises an upper layer data e.g., an IP packet incorporated in the payload, and also a number of IP headers.
According to standard Ethernet protocols (say, IEEE 802.3 and Ethernet II), the minimal length of the Ethernet packet is 64 bytes, while the real information to be transmitted by the packet may constitute some single bytes, for example in a case of voice data.
Some attempts have been made to perform compression of Ethernet packets, for example by introducing a pair of IP-compatible routers (such as Cisco router pair MWR 1900) into an Ethernet link formed between an Ethernet source node and an Ethernet destination node. A simplified block-diagram of such a solution is illustrated in FIG. 3. Owing to presence of the routers, the Ethernet packets can be peeled to drop the Ethernet headers thus obtaining IP packets, the IP packets can further be compressed utilizing the 3rd layer protocol, similar to the principle described above with respect to IP networks. However, such a solution changes the logics of the network and its addressing system; it is therefore both complex and expensive.